Back-pressure valve



Jan. 10, 1928. 1,655,418

H. V. HAIGHT BACK PRESSURENALVE Filed June 16. 1927 Patented Jan.10,1928.

UNITED D'MSTATES.

HARRY v. ,HAIGI-IT, or SHERBROOKE, QUEBEC, CANADA, AssIeNon 'ro IGERSOLL- RAND COMPANY,- OF JERSEY CITY, NEW JERSEY, A CORPORATIONOF-N-EW JER- SEY.

BAcx-rREssUa vALva.

Application filed June 16, 1927. Serial so. 199,292.

' This invention relates tocompressors, but more particularly to abackpressure valve adapted to be interposed in the discharge line ofcompressors actuated by propelling elements nnprovided with means forcontrolling the speed thereof, as tor instance, tangential or impulsewater wheels. The object of theinventionis to maintain a suitable backpressure in the discharge line of acompressor, thus insuringagainstoverspeeding of the compressor during the starting thereof or in theeventthat a break shouldoccur in the discharge line.

, Other objects willbe in part obvious and in part pointed outhereinafter.

The invention consists of the combination of elements and arrangement ofparts having the general mode of operation substantially as hereinafterdescribed and claimed and illustrateclin the accompanying drawing, inwhich is shown a compressor system, in elevation, having the inventionapplied thereto.

Referring more particularly to the drawing, A designates a portion of acompressor of any well known type and B adischarge line leadingtherefrom through which the pressure fluid is conveyed to a storagereceiverC connected to the opposite end of the discharge line B. r

I In accordance with the present invention, means are provided forpreventing overspeedin of the compressor during the starting thereofagainst an empty system or in the event that a break should occur in thedischarge line B. To that end a back pressure valve designated generallyby Dis interposed in the. discharge line B, preferably at a point nearthe compressor A so that that section of the dischar e line B betweenthe compressor A and the back pressure valve D may be of as short alength as possible.

i The back pressure valve D in the present instance comprises a casing Fhaving suitable flanges G at its ends or other suitable means forattaching the casing F to the discharge line B. The casing F in thepresent instance is provided with a U-shaped wall H which divides thecasing intoa pair ot' chambers and K.

Communication between the chambers J and K is afforded through suitableports L and O in. the wall H. The port L isof larger diameter than theport 0 and is preferably; located inthe upper portion of the Wall 1H. 71 V i i In order to control communication between the chambers J and Kavalve design atedfgenerallyby P is disposed in the case ing F andcomprises in this instance a stem Q havinga head Rto control the port Land a smaller head S, to control the portO. a The stem Q is preferablyof a-dia'meter substantially equallingthedifiZerence in area between theheads R andS and projects with its uppermostend T beyondthe top portionof the casing F while the lowermost end U of the stem Q, is disposedslidably in'arecess V in a cover 1 V located in the hottom of thecasingF. J. p v A somewhat similarcover X forms a cl sure for anaperture Y in .the:top of the casing, and in this cover Xis formeda-bore Zto slidably guide the stemQ/of the valve. Communication betweenthe chamber K and the recess V is in this instance altorded through apassage bleeding to the lowermost endof the recess Suitable means areprovided for holding the valve P closed until thepressure inthedischarge line B between the compressor A and the back pressure valve Dreaches certain predetermined value. To that end a cross head or yoke cis attached to the uppermost end of the valve stelnQandvat the oppositeends of the yoke care'supported rods or bolts d' which in turn supportat their lowermostends a'block 6.- The yoke, o is preferably sodisposedwith respectto the casing-F thatthe bolts d are located on oppositesides of the casing F. The block a is intended to be of such proportionsthat its weight, together with the weights of the valve and the elementswhereby the block will be attached to the valve, will substantiallyequal the value of thepressure which it is intended to attain betweenthe compressor and the, back pressure valve D before permitting anypressure fluid to escape into the systembeyond the back pressure valveD.

" :For the sake of simplicity of illustration,

the block 6 isshown asbeing asingle piece.

:It .will be' obvious however, that the block may be divided into aplurality'ofmembers of known weight so that whenever it is v theratedspeedg desired to open the valve P at other pressures, other weightsmaybe added or removed to or from the block a;

The operation of the device is as "follows: Let it be assumed that it bedesired to obtain a pressure in the discharge line 13 between thecompressor and the back pressure valve of, say, sixty pounds, and thatthe diiference in the areas of the heads R and S is approximately onesquare inch. The stem Q, may then be made of such diameter that its areawill also substantially equal the difference in area between the heads Rand S. It then the block 6 of a weight which, together with the weightsof the associated elements, totalling sixty pounds isattached tothe'valve, the said valve P will remain closed until the pressure in thechamber J slightly exceeds the weight of the block 6.

After the pressure in the chamber J reaches a value sutlicient to openthe valve P, pressure fluid will pass through the ports Land 0 into thechamber if; and thus, of

course, into the system beyond the back pressure valve D. After thevalve has been opened pressure fluid flowing into the chamber K willpass through the passage 6 and acting against the lowermost end U of thevalve stem, together with the pressure fluid acting against the head R,will open the valve P to wide limits and will hold the valve in thisposition as long as the pressure in the chambers J and K exceeds theweights of the block 6 and the valve P.

It for any reason the pressure in the discharge system should drop to avalue below the weight of the block and the valve, the valve will againbe closeduntil' the pressurebetween the compressor and the valve Preaches that value at which the valve may again be opened.

The device described herein has been found to be'particularly usefulwhen attached to the discharge line of a compressor actuated bypropelling mechanism in which such mechanism is unprovided with meansfor controlling the speed thereof, as for instance, a tangential orimpulse water wheel. As will be readily understood, a compressor "thusdriven will, when operating against an empty system, run at excessivelyhigh speeds which occasionally prove injurious to the compressor.

The present invention has also proven to be an excellent means forpreventing overspeeding of the compressor in the event or a break in thedischarge line between the valve D and receiver C. In such case, ofcourse, the pressure in the system immediately drops, possibly to nearlyatmospheric pressure, and the compressor speed increases to a rateconsiderably in excess of By means of the present invention occurrencesof the kind described will be averted and the compressor will at alltimes be actuated at safe speeds.

I claim:

1. A. back pressure valve, comprising a casing adapted to be interposedin the discharge line of a compressor, a wall dividing the casing intotwo chambers, said wall having ports of di'lterent diameters affordingcommunication between the chambers, a differential valve controlling theports, a stem on the valve of a cross-sectional area substantiallyequalling the differential of the valve, said stem extending beyond theeasing, and a block supported by the stem holding the valve closed untilthe pressure between the compressor and the valve reaches a valuesubstantially equal to the weight or the block.

2. A back pressure valve adapted to be interposed in the discharge lineof a compressor driven by an impulse propelling element, comprising acasing, a wall dividing the easing into two chambers, said wall havingports of dilferent diameter affording communication between thechambers, a valve having two heads of different diameter controlling theports, a stem of a crosssectional diameterequalling the differential ofthe heads connecting the heads and ex tending beyond the casing, and ablock supported'by the stem holding the valve closed until the pressurein the chambers substantially equals the weight of the block.

A back pressure valve adapted to be interposed in the discharge line ofa compressor driven by an impulse propelling element, comprising acasing having a here at one end and a coaxial recess at the other end, awall dividing the easing into a pair of chambers having ports ofditl'erent diameter ai'i'ording communication between the chainhers, adifferential valve controlling the ports having a stem, of a crossseoti'ma-l. area substantially equalling the dillerential ot the valve, saidstein being slidable in the bore and the recess and extending with oneend beyond the casing, a block carried by the valve exerting a constantpull thereon for holding the valve closed until the pres sure betweenthe compressor and the valve attains a value suiiicient to open thevalve, and a passage in the casing conveying pressure fluid into therecess to act against the end of the stem for holding the valve openafter the pressure in the chambers reaches a value exceeding the weightsof the valve and the block.

In testimony whereof I have signed this specification.

Hea s v- He

